[DOC] Removed false "dataObject" parts from variables and field names

In detail:
 * Quite a few variables, parameters, and fields were named as
"xyActivityDataObject" whereas they were actually referring to
"xyActivity".
 * The methods in AbstractActivityReceiver are sorted alphabetically.
 * Obvious flaws and easy enhancements in existing JavaDoc (around the
changes from above) were fixed/done.

Change-Id: I71ffca53d32661a7f0ac40e0b35f7b78b5291a00
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/856
Tested-by: Jenkins CI
Reviewed-by: Patrick Schlott <pschlottk@gmail.com>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>
Reviewed-by: Franz Zieris <zieris@inf.fu-berlin.de>